Dosage regulator and control wedge for hypodermic syringes



' Oct. 1, 1 0- D. 1. PLETCHER DOSAGE REGULATOR AND CONTROL WEDGEFORHYPODERMIC SYRINGES Filed Feb. 25, 1939 INVENTOR ATTORNEY PatentedOct. 1, 1940 UNITED STATES DOSAGE REGULATOR AND CONTROL WEDGE FORHYPODERMIC SYRJNGES Delmer I. Fletcher, Bakersfield, Calif. ApplicationFebruary 25, 1939, Serial No. 258,425

1 Claim.

This invention relates to an improvement in a control device forregulating the dosage to be given by a hypodermic syringe and fortightening the plunger or plunger rod in the cylinder 5 so that therecannot be any flow of blood or pus into the cylinder or barrel of thesyringe, due to body pressure or abscess pressure, when the pressure ofthe hand on the plunger has been removed.

It is well known to the profession that unless the pressure of the handon the free acting plunger of a hypodermic syringe is maintained or theplunger or plunger rod is tightened, the counter pressure of the bloodor the greater 15 pressure of an abscess will force blood or pus backinto the syringe and thereby contaminate it.

The device shownin my invention is suitable for attachment to any kindof ordinary hypo- 20 dermic syringe, and when it has been attached itwill change any ordinary syringe into a dosage regulating and controlledsyringe.

Hypodermic syringes have an ebb and flow feature during most injections.Free acting 25 plunger rods and rebound from rubber corks and rubberpistons are responsible for most of this condition. When hand pressuredecreases so that tissue resistance is greater than pressure on medicinethe unused medicine becomes contam- 30 inated. A constant flow forwardis necessary during an injection and a controlled plunger rod isnecessary to maintain constant pressure within the barrel of a syringe.With the herein described and claimed control wedge, the dosage 35 maybe predetermined and a positive tension maintained within the barrel orcartridge, thus preventing an invasion or outside elements with themedicine, or back infiltration. With the control wedge, rubber pistonsmay be safely used 4 in glass barrels of various types of constructionand the previously objectionable feature of suction from rebound iseliminated. This dosage indicator is not a locking device as aninjection may be continued, with slightly increased pres- 45 sure, undercontrol, to be discontinued safely at any desired point. This controlwedge is a dosage regulator and tightening device for plunger, thuspreventing reinvasion of outside elements at cessation of hand pressure.

50 Referring now to the accompanying drawing,

which forms a part of this specification and illustrates by way ofexample embodiments of the inventionplunger refers to ground or milledpiston, plunger rod refers to rod used with re- 55 duced head openingand rubber pistons.

Fig. 1 is an enlarged view of control wedge, clasp type.

Fig. 2 is a cross-section of the control wedge with an internal coilspring grip surrounded by a ring for hand adjustment.

Fig. 3 is a topview of the control wedge shown in Fig. 2.

Fig. 4, view of coil spring used for tension in control wedge shown inFig. 2.

Fig. 5 is a view of control Wedge with its tension spring so arrangedthat the wedge can be easily released or removed.

Fig. 6 is an elevation partly in section of a syringe with the controlwedge adjusted to tighten the rod or plunger at the second indicatorline marked on the plunger or plunger rod.

Fig. 7 is a fragmentary view partly in section showing how the controlwedge tightens the plunger, when it comes into contact with the cylinderor head of the syringe.

Fig. 8 is a cross-section view of the control wedge shown on the plungerrod of a syringe in which the plunger rod has a small diameter, as inmetal and cartridge type syringes, with reduced head opening and rubberpistons.

Fig. 9 is a fragmentary elevation of a syringe, showing the controlwedge, plunger and cylinder in cross-section as a milled piston andcylinder.

Similar numbers refer to similar parts in all the figures.

The control wedge i2 is attached to the plunger ill at any requiredposition by tension spring ll, or clasp spring which may be enclosed ina ring [4, shown in Fig. 3, or it may be simply 3 a coiled spring as inFig. 4, or simply a spring clip as shown in Fig. 1.

The control wedge I2 is very thin at its apex, and tapered rearwardly sothat it may enter in the space between the circumference of the plunger18 and the inner wall of the cylinder l3 and tighten as plungeradvances.

As soon as the wedge enters the cylinder or head the increasedresistance to the further movement of the plunger or rod can beimmediately felt by the operator, and a further pressure will sufiice totighten the plunger in the cylinder or head of the syringe and therebymaintain the internal pressure of the fluid against the counter pressureof the body. After engagement of control wedge the cannula can bewithdrawn from the body at any dosage index or the plunger piston may beadvanced under increased pressure and stopped when desired withoutcontamination of the medicant in the syringe.

Having thus explained my invention, I claim:

In a syringe, the combination with a syringe cylinder and plungertherein of a wedge, clipped to the plunger by an encircling spring, theapex of the Wedge pointing towards the cylinder, one side of the wedgeparallel to and adjacent to the plunger, a space between the plunger andplunger guide in the cylinder cap suflicient to allow the apex of thewedge to enter between them when the plunger is pressed into thecylinder for the purpose of locking the syringe, substantially 5 asdescribed.

DELMER I. FLETCHER.

